1. Field of the Invention
The present invention generally relates to projecting a two-dimensional image in color while maintaining low power consumption, high resolution, miniature compact size, quiet operation and minimal vibration and, more particularly, to improving the quality of the image.
2. Description of the Related Art
It is generally known to project a two-dimensional image comprised of pixels on a screen based on a pair of scan mirrors which oscillate in mutually orthogonal directions to scan a laser beam from a laser over a raster pattern. The laser beam is incident as a beam spot on one of the mirrors, for example, a horizontal scan mirror, to sweep the beam spot along a horizontal scan line extending along a horizontal scan direction. The horizontal scan line is incident on the other of the mirrors, i.e., a vertical scan mirror, to sweep the scan line along the vertical direction, thereby creating the raster pattern. Turning the beam spot on by energizing the laser, as the beam spot is swept along each scan line, causes selected pixels in each scan line to be illuminated and rendered visible, while turning the beam spot off by deenergizing the laser causes the remaining pixels to be non-illuminated. The illuminated and non-illuminated pixels comprise the image being projected.
Although generally satisfactory for their intended purpose, the known image projection arrangements project the image with limited resolution, typically less than a fourth of video-graphics-array (VGA) quality of 640×480 pixels and, moreover, the quality of the image is somewhat degraded, especially when the image is rendered in color from red, blue and green laser beams emitted from individual red, blue and green lasers. The maximum brightness of each color in an illuminated pixel is limited by the maximum output power of the correspondingly colored laser. The contrast of each illuminated pixel is affected by ambient light levels. Polarized screens are sometimes employed to reduce the effect of strong ambient light, but this option has not been available to laser-based projection arrangements where the lasers emit laser beams of different polarizations.